Honestly, I think people still like to rip on Detroit because it's Detroit, even though they're a basement dweller right now. 25 years of kicking in their teeth has bred some ill will among fans across the league.
I think Toronto signing Tavares should be a fine move. What they need to do is pare back a forward or two in an effort to make cap room to build that blueline. Take Tavares off that team and who is the second center? Kadri has shown to be a guy a team can't depend on, and Nylander is better on the wing (but so was Flip, so maybe). With Tavares and Matthews up the middle, they should be able to spend less on the wings because those two will carry whoever is with them.
It's really something I think the wings need to pay attention to because, as you mention, AA and Mantha will be looking for pay days. Do we really want to lock in on big money wings for 5+ years? Or do we want to move at least one of them to keep some cap space to play with and try to pull in some better assets to build around Larkin, Zadina, Seider, etc.? Maybe the Wings sign both and look to move one later when there's more of a pressing need to make a move.